When a transistor transmits or receives a signal, a swing of the signal will cross all parasitic junction capacitors existing between a doping area of a drain (a source) of the transistor and a substrate for forming the transistor. Because the parasitic junction capacitor having the minimum capacitance value may also have a maximum voltage drop, a corresponding parasitic diode is easily turned on, resulting in the swing of the signal being significantly limited. Because the swing of the signal is significantly limited, power delivered by the signal is also significantly limited. Therefore, how to design a transistor which can increase a range of the swing of the signal becomes an important issue.